For many years it has been the practice to construct truck bodies as structural units substantially independent of the chassis of the motor vehicle. In other words, the body has been designed as a self-supporting structure which was intended to be lifted on to the chassis and tied or bolted down on the chassis at only wisely spaced intervals.
This construction approach most often dictated that the deck, or floor pad, of the truck body be constructed with a reinforcing substructure of transverse and longitudinal crossbeams to give the truck body sufficient strength and rigidity. U.S. Pat. No. 2,100,323, granted Nov. 30, 1937 to B. F. Fitch for "AUTOMOTIVE TRUCK BODY" discloses a truck body utilizing this construction technique. The presence of such deck substructures has resulted in the deck being positioned a significant distance above the vehicle chassis and, hence, a substantial distance above the road surface.
Except for very large trucks and semi-tractor trailers intended to be loaded from elevated loading docks, the farther the truck body deck is above the road surface the more effort must be exerted to load the truck. This is a very practical consideration in rental truck fleets, for example, where it is expected the truck will more often then not be loaded by inexperienced personnel using an inclined ramp. The goods are usually carried, one at a time, from the road surface up the ramp and into the truck. If the truck body deck is even a few inches higher than it actually need be, undesirable loading effort must be expended.
There has been another undesirable aspect of body deck mounting in the prior art growing out of irregularities in the mounting surface of the truck chassis, i.e. the upper surface of the longitudinal frame members of the chassis. Such irregularities are caused in some instances merely by the presence of rivet heads or other fastener elements on the upper surface of the frame members. These protuberances and other irregularities have led to the practice of providing deformable spacers, such as wood strips, between the chassis frame members and the body deck structure. This, of course, further increased the elevation of the deck above the road surface. A representative structure of this type is described hereinafter in the Best Mode section of this specification to contrast that structure with the present invention.